On 08/26/2015 04:26 PM, Dave Young wrote:
>On 08/26/15 at 04:18pm, "Zhou, Wenjian/周文剑" wrote:
>>Hello Dave,
>>
>>On 08/26/2015 03:59 PM, Dave Young wrote:
>>>Hi,
>>>
>>>On 08/25/15 at 04:43pm, Zhou Wenjian wrote:
>>>>A new feature that doing compressing and writing by multi-threads
>>>>has been added in makedumpfile. The thread num is specified by
>>>>"--num-threads NUM". According to its implementation, there
will
>>>>be performance degradation if the threads are more than cpus.
>>>>So we should check it.
>>>>
>>>>Signed-off-by: Zhou wenjian <zhouwj-fnst(a)cn.fujitsu.com>
>>>>---
>>>> kdumpctl | 15 +++++++++++++++
>>>> 1 files changed, 15 insertions(+), 0 deletions(-)
>>>>
>>>>diff --git a/kdumpctl b/kdumpctl
>>>>index b504734..fd2abe4 100755
>>>>--- a/kdumpctl
>>>>+++ b/kdumpctl
>>>>@@ -259,6 +259,21 @@ check_config()
>>>> esac
>>>> done < $KDUMP_CONFIG_FILE
>>>>
>>>>+ grep "^core_collector.*makedumpfile" $KDUMP_CONFIG_FILE |
grep -q "num-threads"
>>>>+ if [ $? -eq 0 ];then
>>>>+ local nr_cpus=1
>>>>+ local num_threads=0
>>>>+ local core_collector=`grep "^core_collector"
$KDUMP_CONFIG_FILE`
>>>>+
>>>>+ num_threads=`echo ${core_collector#*--num-threads} | awk '{print
$1}'`
>>>>+ nr_cpus=`echo ${KDUMP_COMMANDLINE_APPEND#*nr_cpus=} | awk '{print
$1}'`
>>>>+
>>>>+ if [ $num_threads -ge $nr_cpus ];then
>>>>+ echo "The num_threads:$num_threads(specified in /etc/kdump.conf)
should be less than nr_cpus:$nr_cpus(specified in /etc/sysconfig/kdump)"
>>>>+ echo "or makedumpfile may have bad performance!"
>>>
>>>It is better to do this in makedumpfile source code instead of adding
>>>these warnings specific for num-threads here.
>>>
>>
>>I have one more question.
>>Since multi-thread feature is associated with nr_cpus, should we do something
here?
>
>Hmm, adding it in makedumpfile will be too late for warning users. But I do not like
>adding these stuff in distribution script, user should know the limitation if he
>choose the thread number. How about moving it to makedumpfile --help to describe
>the problem just around the num_threads option.
>
Whatever, we should not introduce nr_cpus in makedumpfile --help.
I noticed a discussion between Vivek and Hatayama.
(You can refer to
https://lists.fedoraproject.org/pipermail/kexec/2014-March/000687.html)
I think finishing that patch may help.
I will post the patch later.
Please give me some comments on the later patch.
I'm fine to add something in kexec kdump howto document, it is better than adding
more logic in kdumpctl.
Why do you think it is bad to add it to makedumpfile? Maybe makedumpfile manpage?
Thanks
Dave